Placentitis in Central Kentucky broodmares

Abstract

Feto-placental infection caused by microorganisms was the most common cause of death of fetuses, stillborn foals, and foals that died within 24 hrs after birth in central Kentucky. Pathologically, three types of placentitis were seen: ascending, diffuse, and focal mucoid. The pathogenesis in each form is believed to be different and each is associated with certain types of causative bacteria or fungi. Ascending placentitis was the most common type of placentitis prior to the 1998 foaling season in Kentucky. This form is thought to be the result of microorganisms gaining access to the cervical portion of the placenta during gestation by spread from the lower reproductive tract through the cervix. Streptococci and E. coli were the most commonly isolated bacteria. Diffuse or multifocal placentitis was less commonly diagnosed and is associated with hematogenous spread of microorganisms to the uterus of the mare with subsequent infection of the placenta. This form was associated with infection by bacteria in the genera Leptospira, Salmonella, Histoplasma, and Candida. Focal mucoid placentitis is also known as nocardioform placentitis. Nocardioform placentitis has emerged as the most commonly diagnosed type of placentitis over the last two foaling seasons and is characterized by unique pathology and distinct bacteria. At present the pathogenesis of this form is unknown. Diagnosis of placentitis during gestation is often difficult. Most mares show no outward signs of infection. Some mares will undergo premature mammary development with lactation and, occasionally, a vaginal discharge is present. Transrectal and transabdominal ultrasound examinations are useful in arriving at a diagnosis if placentitis is suspected. Various treatment modalities have been utilized in an attempt to maintain gestation for as long as possible to enhance foal viability. Placentitis results in several outcomes. In addition to abortions and stillbirths, the mare may produce small weak foals or normal foals. The small, weak neonates represent a special management and medical challenge. These individuals have an increased risk of sepsis and orthopedic problems requiring extensive care.